1. Field of the Invention
Embodiments of the present invention generally relate to magnetoresistive sensors. Specifically, embodiments of the invention relate to magnetoresistive sensors, methods for manufacturing magnetoresistive sensors, and apparatuses using magnetoresistive sensors.
2. Description of the Related Art
Modern computer systems typically include a hard drive which may be used as mass storage for the computer system. Information in the hard drive is typically stored by changing the magnetization of areas on one or more magnetic disks within the hard drive. To read the information, the hard drive typically includes a magnetoresistive sensor which senses the magnetic fields from the magnetized areas as the magnetic disks spin beneath or above the magnetoresistive sensor.
Modern magnetoresistive sensors typically include several layers of material deposited on a base layer. As the magnetoresistive sensor passes over a magnetized area of a magnetic disk, the magnetic field from the magnetized area may induce a detectable change in the layers of material in the magnetoresistive sensor. For example, during a read operation, a current may be applied to the layers of material in the magnetoresistive sensor. The current applied to the layers of material may create a voltage across the layers of material which is proportional to the resistance of the layers of material. As the sensor passes over a magnetic field of a magnetized area on the magnetic disk, the magnetic field may cause a change in the combined resistance of the layers of material (e.g., an increase or decrease in the resistance of the layers of material). The magnetic field of the magnetized area may then be measured via a corresponding change in the voltage across the layers of material (e.g., a corresponding increase or decrease in the voltage resulting from the current applied to the layers of material).
In some cases, the magnetic field within a magnetoresistive sensor may experience instability due to operating conditions (e.g., the current applied to the sensor, the temperature of the sensor, and/or previous magnetic fields applied to the sensor) in which the sensor is used. Instability in the magnetic field of the sensor may degrade read operations performed with the sensor by increasing noise in the read signals obtained from the sensor. Accordingly, to improve operation of the sensor, there may be a desire to improve the magnetic stability of a magnetoresistive sensor. However, increasing the magnetic stability of the magnetoresistive sensor may also reduce the sensitivity of the magnetoresistive sensor by reducing the ability of the magnetoresistive sensor to respond to magnetized areas of a hard drive disk.
Therefore, what is needed is a magnetoresistive sensor which provides increased magnetic stability without reduced sensitivity and a method for making the magnetoresistive sensor.